Total Rebuild Help

[SSOWDERS]

Well, after reading this forum for quite some time. I decided to begin a total rebuild on a 1979 Cobia Sanlando bowrider that has been part of the family. Sole, stringers, transom, broken glass, and gel coat cracks to name a few things on my agenda. Anyway, I have removed the top cap and taken out the rotten transom. The stringers were cut back about 18 inches for some working room and to free up the bottom portion of the transom for removal. Also glassed to the transom and the side of the hull in both back corners were some fiberglass boxes that were filled with foam. Had to remove those as well. They were also glassed on the bottom to a fiberglass skin that covered the stringers and foam under the sole of the entire boat. The boxes were approximately 26 1/2 inches long, 14 inches wide, and 14 inches tall. I understand that the foam is a flotation requirement, but my question is this: Should I replace those boxes or leave them out? They did seem to add a little structural integrity to the sides of the hull when they were in place. I plan on replacing the foam in other places on the boat. I'm just not real sure how I would build those boxes back should I need to put them back in. Any ideas on that would also be greatly appreciated. Thank you all in advance for your help and wisdom! I will be posting some pictures of my progress and frustrations throughout this project.

 

[jbcurt00]

Re: Total Rebuild Help

Pix from before the demo may help, and for sure some as the hull sits now....

Reference photos from Cobia brochure may help, be right back

EDIT:
Like these boxes:

This ^^^ is a 1980 15' Sanlando, may or may not be similar.....

Although they were probably primarily for floatation foam, I suspect that as cost cutting measures, since the foam was required, the boxes also functioned as structural elements. Since Cobia HAD to have the flotation foam, if they could reduce the material usage in adjoining areas & maintain hull integrity, they certainly could. That's why I think it's 1 of the reasons there are so many foam filled hulls that are in such poor overall condition. The foam was an integrated structural element, which allowed material reductions in other areas. Once the foam became compromised, the stringers, hull, transom & deck quickly followed...

You may need the box volume for flotation foam as well, but I'd put them back for structural reasons for sure.

Welcome to the iboats dry dock. And post up whatever pix you can. Using photobucket imbeds the pix nice & large & in your thread, which makes it easier to follow text descriptions.

 

[SSOWDERS]

Re: Total Rebuild Help

Thank you for your response! Yep... the boxes look exactly as the ones in the picture you posted. I will try and get some uploaded within the next day or two to show where I started and where I am at now. I kind of figured they had some structural value. The sides of the hull seemed to have a little more flex once they were removed. That's why I was concerned. Just don't know quite the best plan to rebuild them when I get to that point since they were glassed to a fiberglass skin that ran under the plywood throughout the boat. I don't plan on replacing the skin in that way. Was just going to glass over the top of the new plywood that I put in. I didn't want to glass them back in on top of the plywood on the chance that the sole may have to be replaced again at some point. Then the boxes would have to be removed once again. Still trying to figure out the best way to put them back in. Maybe I am overthinking this.... Thanks again!

 

[SSOWDERS]

Re: Total Rebuild Help

After another 4 hours of grinding today (12 total so far), I uncovered another question(s) for the experts. I noticed some hairline spider cracks in the hull. In some areas they look like alligator skin. You can actually feel the roughnes when you run your hand over them. There is a thick coat of resin that exists on top of the woven roven that the hull is made of. It is almost yellow in appearance. Anyway, I ground down an area that contained some of these cracks and they disappeared right as I reached the actual woven roven. So, I'm assuming these cracks are in the thick resin itself that is on top of the mat. By the way, there are numerous areas like this all over the bottom of the hull. Here come the questions: 1) Is this normal for an old boat? 2) I'm assuming that this will lead to future problems, correct? 3) What is the best fix? I'm thinking of grinding down those areas and adding a layer of 1708 over them. That means I will pretty much have to grind the whole bottom of the boat. Not something that I would look forward to, but will if I have to in order to save it. If I do have to go that route, do I grind all the resin off down to the mat or do I just grind a portion down to give the new resin something to grip to and not actually remove all the spider cracks in the resin? I hope I'm making sense. I cannot find the usb cable for my camera so until I go get another one I cannot put up any pics just yet. I know, I'm making things difficult. Thanks in advance!

 

[ondarvr]

Re: Total Rebuild Help

Having cracks like that isn't uncommon, it is from sloppy workmanship, there should be no extra resin build up anywhere. Resin is weak and brittle by itself, so when it gets stressed or flexed it cracks easily.

You should grind the cracks out and remove any extra resin even if it's not cracked right now, then replace any glass you removed, you don't really need to add more glass than what was originally there unless it failed in some way.

 

[SSOWDERS]

Re: Total Rebuild Help

I appreciate your input. Those cracks had me a bit worried! Looks like I have a lot more grinding to do to remove the excess resin. But, in the end it will be worth it. When I grind it down it does expose the woven roven underneath. I have to go a little deep to remove the cracks completely. I assume that if that is the case I should just add a thin layer of CSM at that point for protection? There doesn't appear to be any damage to the actual glass after I grind it down though.

 

[SSOWDERS]

Re: Total Rebuild Help

Finally got a cord for the camera so I figured I would put up some images of my project.

Hopefully they uploaded ok. Guess we will find out!

 

[SSOWDERS]

Re: Total Rebuild Help

Does anyone know what these round discs are for? I have found a total of 4 of them glassed to the hull so far. One in each of the boxes in the rear of the boat and one each next to the outside stringers. Two popped loose and they don't seem to be any type of patch. Just curious to find out if they have any purpose.

 

[jbcurt00]

Re: Total Rebuild Help

Does anyone know what these round discs are for?

W/out more info I don't know what they're for, but my 1st guess would be the plugs cut out of the deck to allow pour-in foam to be poured below deck. And they happened to get left in the hull when the final layer of fiberglass was shot on (if it was put down w/ a chopped glass gun) or dropped on wet resin during layup.......

 

[SSOWDERS]

Re: Total Rebuild Help

I was hoping that would be the case. Finally had some time to get back to the boat. Here is a picture of the cracks in the resin on the hull of the boat. You can see how thick the resin was that they put down. Almost like they just slopped it on there. When I grind out those cracks in the resin it goes all the way down to the woven roven as you see here. Am I doing this correctly? I have only done a small spot so far. Also, I assume that I would have to put another layer of at least CSM over where I grind out the old resin for protection. On the topic of grinding, is it necessary to grind out all the old tabbing for the stringers - or just to get it back smooth again. I am wondering because it seems this would create a big build up of tabbing if it isn't totally removed causing possible high stress areas to the hull. Or, will the new tabbing just displace the stress over the old tabs. Just trying to make sure I get this right. Any words of wisdom would be appreciated!

 

[SSOWDERS]

Re: Total Rebuild Help

Well, got some more work done on the boat today. Digging out foam and grinding..... don't know a better way to spend a Monday off. In case anyone is wondering, a stripping disc on the grinder works much quicker and covers more surface area than a grinding disc I found. They just wear out pretty quickly. Maybe everyone already knows that. Anyway, here is the foam removed around the entire stringer length for the most part. There seemed to be a layer of CSM on each stringer, but the original install is horrible at best. There were huge air gaps between the woven roven and the stringer sides when it was installed. The only place the roven actually touched the stringer was on the top in most cases. Wow! I cut a section of glass away to take a look at what remained of the stringers and here is what I found. Yep. Just air with a pile of dirt along the hull wrapped by glass. Totally rotted away. The glass that wrapped the stringers was actually starting to compress down and bulge at the top. I also was able to grind out the rest of the old wood that remained on the transom. How does this look? I still have some touch ups to do in the corners where the grinder wouldn't get in there. Will probably use a Dremel with grinding attachment. And yes..... despite my best efforts I managed to grind a bit too much in a small area and hit gell coat. OOPS! At least it can be fixed. Will be back at it tomorrow and see what I can get done. The task seems so huge. But, one day at a time I guess. I will just keep plugging away!

 

[SSOWDERS]

Re: Total Rebuild Help

Haven't really had much interest in my project, but I will continue with this thread just in case it helps someone out in the future. Got a few more hours on the boat today before it was brought to my attention that all my free time was spent on it lately. I guess I will have to do a better balancing act with this. Anyway, I have pretty much completed grinding one half of the boat and the transom area. I am doing it this way as I will be replacing only one stringer at a time. Despite my best efforts to brace the hull during this process, it still gives when I walk on it in spots. This leads me to 2 conclusions: 1. the foam under the sole was structural so it will all be replaced and 2. only do 1 stringer at a time to avoid warping the hull. One more day of clean up grinding and it will be time to get some plywood for the transom and the stringer I have removed. I will be using two pieces of 3/4" plywood for the transom laminated together with PL Premium adhesive. I figured if it was good enough for Friscoboater it was good enough for me. His thread is very helpful. For the stringer I am going to use regular pine. It will be encased in 1.5 oz. CSM after a good resin soak prior to install and then glassed in so that should keep it plenty protected. I did notice that the sole on this boat had to have been replaced before. Is it possible the original was only 1/4" thick plywood? The reason I say this is that after originally removing the plywood under the carpet it was on top of a fiberglass skin. After cutting out that skin there was foam. I didn't think about it at the time, but the foam had a bunch of "thick dirt" on top of it about 1/4" thick. I am guessing that the original sole was glassed into the boat, but it rotted so badly it turned into what appeared to be a dirt layer. This messed with me a bit when I was trying to make sure I marked and measured stringer heights, deck height etc. But I think I got it now. Thanks for taking a look. Please feel free to chime in with any suggestions or oversights that I may have made or am about to make. Time for a cold one and trivia night!

 

[Woodonglass]

Re: Total Rebuild Help

The first link in my signature has some drawings an details on how to do your transom, stringers and deck. I would not recommend pine for your stringers. I'd use the same plywood that you use for your transom. I would also not recommend using PL to glue the transom pieces together. TiteBond III wood glue is 100% waterproof and will cure in 24 hours. PL will take 3-4 days. I've never seen a 1/4" thick deck. Not saying it wasn't just I've never seen it. I'd recommend a minimum of 1/2" and prolly 5/8" is the best choices.

 

[GT1000000]

Re: Total Rebuild Help

Hello SSOWDERS,

A belated welcome to the dry dock...Just got caught up with your thread and I see you have done your homework...A+...

Your progress so far is excellent and it seems you have most everything under control...

My only suggestion so far is instead of using PL Premium to glue the two transom plates together, you could use Titebond III or Gorilla Glue...they are both waterproof and will be dry and ready to use in 24 hours, as opposed to the 72 hour cure time of PL...your choice...

Other than that carry on, you are doing a great job so far...

I will tag along to learn, cheer, and help in any way I can...

Best regards,
GT1M

 

[SSOWDERS]

Re: Total Rebuild Help

Thanks GT and Woodonglass for checking in on me! I know there are a ton of people out there looking for help with there boats and they definitely came to the right place. Plenty of knowledgeable and helpful people here and it is appreciated.

Been sitting here for 2 hours waiting to see if it is going to rain. I know the minute I go outside the sky will open up and downpour. I do hope to get some time in today.

Titebond III it is. I did look at that stuff when I was making my every other day Lowe's trip. Just seemed kind of thin. But, if you guys say it's the stuff to use I trust your expertise that's for sure.

If it does rain I guess I will mess around with my Photobucket account and see if I can get my pictures to post larger. I tried briefly the other day and they still posted thumbnail size. Didn't really get into it though. Wanted to get back out to the boat! I will check back later this evening. Hopefully I have some progress to report.

BY the way GT, I am on page 27 of your thread. Great job!

Thanks!

 

[Georgesalmon]

Re: Total Rebuild Help

Those little round discs may have been pulling blocks used to demold the hull from the mold. Not needed now. You realyl should replace the flotation exactly where you found it. The location is important to the "level" flotation part. If you add the same amount of foam somewhere else the boat might still float but with only the tip of the bow pointing up. They were back there to keep the stern level with the bow and located above the deck to keep the hull from rolling over in a catastrophe to give the survivors something to grab on to. Remember that's where the motor is.

 

[Woodonglass]

Re: Total Rebuild Help

TB III is a great glue for laminating plywood. It only requires a thin layer on BOTH sheets. Dump the glue on and use the smallest grooved trowel you can find 1/16 - 1/8" to spread it. Then follow up with a 6" FOAM roller to get 100% coverage, again, on Both sheets of plywood. Then use deck screws to screw it together and let the screws act as your clamps. If you space the screws 4-6" apart it will be awesome strong. Put it on the garage floor with some heavy weight on it to make sure it stays flat during the curing process. 24 hours and you're good to go to put the resin and CSM on it.

 

[SSOWDERS]

Re: Total Rebuild Help

Thanks for the input Georgesalmon. Much appreciated explaination! The foam is definitely going back in.

Great tips Woodonglass. That is precisely what I will do.

Having help sure makes this project much more manageable. Still have a long way to go though.

I did manage to get about 3 hours in today before the skies didn't cooperate. I think the wife conjured up some rain so I would have to come in instead of being out there all day today. I do have a new nickname though. I am affectionately known as Pig Pen now. Due to the trail of dust I leave behind when I walk around. Grinding is so much fun! I keep telling myself that anyway. I'm getting plenty of practice at it.

Here is the progress I made today

I am starting to get together my supply list. I will be using Poly resin. I know the debate, but have chosen to use it. I can pretty much calculate the amount of 1.5 CSM and 1708 I will use plus waste and practice pieces (never glassed before). I also have a listing of how much resin is needed for each. However, I could use some help on estimating the materials for making PB for transom install and fillets around it and the stringers. The transom is 61" wide and 19" deep at the deepest point. The two outer stringers are 10" long and 4" at the deepest. The center stringer is 12' long and 7 inches at the deepest. Not sure if that was needed or not for what I am asking. So, how much resin, Cabosil, and CSM fibers will I need ballpark for fillets and transom install? I'm not sure how much PB it will take or how much of each you add to make the PB itself. Any help is much appreciated!

Oh, one more thing. I had to grind out a bunch of old resin that was cracking all over the hull since it was so thick. Please take a look at this picture.Did I go down too far? Should this be coated with a thin layer of resin or CSM or will it be fine as is. I am concerned as the roven is exposed.

Thanks again everyone!

 

[Trooper82]

Re: Total Rebuild Help

Looking purdy on the SB side....not a pro here, but I would suggest a layer of CSM followed up with 1708 in layers where you took that resin out...enough to bring it back to thinkness if you went down multiple layers...I'm sure others will chime in..

 

[Woodonglass]

Re: Total Rebuild Help

For your PB it should take approx 3 qts of resin and 4 qts of Cabosil and 3/4 cup of Chopped milled fibers to do the transom install and filleting. To bed the stringers another 2 qts. Filleting around the Deck, depending on the sized of the gap another 2-3 qts. Based on this I'd say about 2 gallons of resin 3 gallons of cabosil and 3 cups of CMF. Trooper is spot on on what to do about reinforcing the hull.